The invention relates to a method for determining the desired ventilation air temperature of an automatic heating and air-conditioning system of a vehicle, preferably a convertible, wherein the open or closed state of the vehicle's top is detected.
Currently many vehicles are equipped with a heating and air-conditioning system, which enables the occupants to heat or air-condition, as desired, the interior of the vehicle while the vehicle is closed. If the heating and air-conditioning system is an automatically controlled heating and air-conditioning system, all manipulations of the heating and air-conditioning system are performed automatically as a function of the adjustments made by the vehicle occupants. In openable vehicles—for example, convertibles—the automatic control and/or regulation is usually carried out the same way when the top is open as when the top is closed. The result is that the vehicle occupants switch off the automatic heating and air-conditioning system, since it does not automatically react to the new requirements of the vehicle occupants.
German Patent Document DE 197 47 326 A1 discloses an automatic air-conditioning system, which automatically switches off when the folding top is open. The vehicle occupants could, in fact, perform the adjustment manually, but that would require a great deal of effort to operate due to the continuously changing boundary conditions, such as the incoming sunlight intensity.
German Patent Document DE 38 43 898 C2 describes a method for controlling a heating system for vehicles that have tops that can be opened and closed. When the top is closed, an interior temperature control mode for setting the temperature mixing flaps as a function of the interior temperature, the desired temperature and the ventilation air temperature is enabled. When the top is open, a switch is made to a ventilation air temperature control mode, in which the temperature mixing flap is adjusted only as a function of the desired temperature and the ventilation air temperature. Therefore, the interior temperature sensor no longer has any effect on the control unit.
Furthermore, US Patent Document 2001/0045278 A1 discloses an automatic air-conditioning system for a vehicle, in which, when the top is open, the blower output is increased by a speed-dependent offset value. In a special design of the air-conditioning system, the top-open blower output is increased by the speed-dependent offset value, only if the outside temperature is within a predefined outside temperature range.
The present invention provides methods to improve—in terms of the requirements of the vehicle occupants—the control and/or regulation of a heating and air-conditioning system for vehicles that have a top that can be opened and closed.
An exemplary inventive method for determining the desired ventilation air temperature of an automatic heating and air-conditioning system of a vehicle, preferably a convertible is explained. In the method, an open or closed state of the top of the vehicle is detected, and the heating and air-conditioning system is controlled and/or regulated in a number of different ways as a function of the state of the top. The exemplary method includes determining the open state of the top, and setting the desired ventilation air temperature at the ventilation flaps as a function of the speed of the vehicle. The vehicle opening, which is called here the top, can include, for example, the top of a convertible, a panorama glass roof, a sun-roof, a moon-roof or a folding top.
The desired ventilation air temperature of the exemplary automatic heating and air-conditioning system is defined preferably as the desired ventilation air temperature at the ventilation flaps of the heating and air-conditioning system. The ventilation flaps, which are a part of an air distribution unit in the vehicle, may be disposed above the leg room flaps and are used for optimizing the temperature control of the vehicle occupants in the upper areas of the body. Owing to the modified surrounding situation, a vehicle occupant, who is sitting in a vehicle the top of which is open, perceives, as compared to sitting in a closed vehicle, other and/or more influencing variables, such as the wind caused when the vehicle is moving. For this reason the state of the top of the vehicle is detected, and the temperature is automatically controlled and/or regulated as a function of the state of the top in a number of different ways, so that the vehicle occupant obtains a temperature control of the interior of the vehicle that is adjusted to the new surrounding situation, and is comfortable for him.
Since the top-open vehicle speed is a significant factor with respect to the temperature perception of the vehicle occupant, the embodiments of the invention provide that the top-open desired ventilation air temperature may be specified and/or controlled in various ways as a function of the speed of the vehicle.
In the open state of the top, the desired ventilation air temperature is determined in such an advantageous exemplary manner that the top-closed desired ventilation air temperature, in particular the desired ventilation air temperature at the ventilation flaps, is increased by a speed-dependent offset value. Therefore, the energy losses, which result from the top being open and which increase as the speed of the vehicle increases, are compensated for by increasing the desired ventilation air temperature. Instead of superimposing the offset value, the top-open desired ventilation air temperature can also be determined, for example, by a characteristic curve or a computational routine that is filed or stored in a control unit.
In one embodiment, since the energy losses at low speeds are relatively small, it is advantageous for the speed-dependent offset value to be approximately zero when the top is open and the speed falls below a predefined first speed threshold value. Thus, when the offset value is set to zero, the desired ventilation air temperature with the top open and at low speeds of the vehicle is equivalent to the desired ventilation air temperature when the top is closed.
In the open state of the top and at a speed ranging from a predefined first speed threshold value to a predefined second speed threshold value, the predefined first speed threshold value being less than the predefined second speed threshold value, it is advantageous to increase, according to a ramp having a constant slope, the speed-dependent offset value, from zero to a maximum offset threshold value, according to an embodiment of the invention.
Since at very high speeds the energy losses stay approximately constant, with the top open and at a speed that exceeds a predefined second speed threshold value, it is advantageous for the exemplary speed-dependent offset value to assume a predefined constant offset threshold value.
In addition, when the top is open, a different desired ventilation air temperature can be specified as a function of the outside temperature. The desired ventilation air temperature can be determined, for example, such that when the top is open, the top-closed desired ventilation air temperature is increased by a speed-dependent and outside temperature-dependent offset value. The speed-dependent and outside temperature-dependent offset value may be the product, for example, of a speed-dependent offset value and an outside temperature factor.
Thus at very high outside temperatures, setting the outside temperature factor to zero does not load the desired ventilation air temperature with a speed-dependent offset value, since at these temperature ranges the desired ventilation air temperature is usually already defined adequately high. Instead of setting the outside temperature factor to zero, this factor can also assume a negative value. Therefore, according to this embodiment, when the top is open in this condition the desired ventilation air temperature becomes smaller than when the top is closed.
At an outside temperature that ranges from a predefined first outside temperature threshold value to a predefined second outside temperature threshold value, the first outside temperature threshold value being less than the second outside temperature threshold value, the speed-dependent offset value may be advantageously multiplied by an outside temperature factor, which becomes larger, according to a ramp, from the first predefined outside temperature threshold value up to the second predefined outside temperature threshold value.
The outside temperature factor may preferably have a value between zero and one. Thus, the top-open desired ventilation air temperature may be increased by a speed-dependent and outside temperature-dependent offset value, which can assume a value of zero up to a value that is equivalent to the speed-dependent offset value without considering the outside temperature.
The position of the window panes and/or a wind deflector of the vehicle can also be detected, for example with sensors, according to another embodiment of the invention. In addition, the desired ventilation air temperature can be controlled as a function of the position of the window panes and/or the wind deflector. As stated above, when the top is open a vehicle passenger reacts to the surrounding situation (temperature, incoming sunlight, wind conditions, blower) much more intensively than in a closed vehicle and/or a convertible with the top closed. The position of the window panes and/or the wind deflector can also be a factor in the occupant's perception of comfort owing to the air currents generated. Therefore, it is advantageous in one embodiment to detect the position of the window panes and/or the wind deflector, and to adjust accordingly the control unit of the heating and air-conditioning system primarily with respect to the control and/or regulation for specifying the desired ventilation air temperature, in particular the desired ventilation air temperature at the ventilation flaps.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.